Process and apparatus for producing compost

ABSTRACT

A process and apparatus for producing compost having a high nutrient value from a mixture of moist, at least partially particulate organic matter containing aerobic bacteria. The composter has two parallel shafts (24,26) with radially projecting fingers (38) which, when the shafts are rotated, slowly and gently churn and agitate the mixture in the composting chamber (10) while air is directed therethrough at a predetermined low rate. When the composting action is completed the compost is promptly dried and packaged in moisture impervious containers.

TECHNICAL FIELD

This invention relates to a method and apparatus for making compost fromorganic matter.

The object of this invention resides in the provision of an economicalmethod and apparatus for producing an organic compost which is not onlyan excellent soil conditioner, but which, unlike most organic composts,has a relatively high fertilizer value and in certain cases is useful asan animal feed.

BACKGROUND ART

Many processes and various types of equipment have been proposed andused heretofore for making compost from animal waste. To my knowledgesuch equipment and processes have had one or more drawbacks ordisadvantages. Some of the equipment heretofore used or proposed isextremely costly and impractical. Likewise, the prior art processes forthe most part involve a relatively long period of time to complete thecomposting action and produce a compost having a relatively low nutrientvalue, especially with reference to its nitrogen content.

Organic waste is converted into compost by the process of fermentation.The waste is usually mixed with organic carbonaceous filler materialand, when the mixture is agitated and aerated, the process offermentation progresses through several states to decompose the mixtureand produce the compost.

The first stage of the fermentation process is characterized by theproduction of and multiplication of aerobic bacteria in the presence ofmoisture and air. This reaction generates heat and the decomposition isthen continued by thermophilic aerobic bacteria. With proper control ofthe moisture content and aeration, heat is generated as the mixturedecomposes and the temperature of the mixture progressively rises to anoptimum value. The mixture remains at this elevated temperature whilethe decomposition process continues for a period of time, depending uponsuch variable conditions as moisture content, manner and extent ofaeration, and the nature of the mixture ingredients. Thereafter themixture gradually cools. When the mixture reaches a predetermined lowtemperature (usually considered to be about 100° F.) the production ofaerobic bacteria ceases and the reaction then becomes anaerobic whereanaerobic bacteria and fungi take over and further decompose the themixture, particularly the cellulose therein, in the presence ofmoisture, but without further aeration required.

I have determined that the maximum nutrient value of the compost isobtained at the completion of the aerobic thermophilic reaction,provided the reaction proceeds under optimum operating conditions. If,after the aerobic reaction is completed, the mixture is permitted toundergo an anaerobic reaction for a prolonged period of time, thenutrient value of the compost (the nitrogen content in particular)actually decreases. In accordance with the present invention themoisture content of the compost is reduced to a predetermined maximumvalue by drying the compost within a reasonably short period of timeafter the aerobic reaction is completed. As a practical matter and forreasons of economy the compost is permitted to cool to room temperatureor about 100° F. in the composting chamber. The compost is thentransferred to a dryer where its moisture content is reduced to lessthan 50% by weight and is thereafter promptly packaged in containerswhich are generally moisture impervious so that the anaerobic reactionis arrested and prevented from re-occurring. In this manner I have beenable to produce compost having a nitrogen content as high as 18% andconsistently higher than 7% from a mixture containing approximately 4%chicken manure and 60% sawdust in a period of 30 to 40 hours.

I believe that the high nutrient value of the compost and the relativelyshort period of time involved in producing the compost according to thepresent invention is also attributable to the manner and the extent towhich the mixture is aerated. The aerobic thermophilic reaction ismaximized when all portions of the mass are slowly aerated uniformly andto the proper extent. In order to aerate the mixture properly it isnecessary to agitate the whole mass very slowly in such a manner thatsubstantially all portions thereof are exposed to an optimum amount ofair for an optimum period of time. If the mass is agitated too violentlyor if the amount of air is excessive, the mixture will be dried andcooled. On the other hand, if the air supplied is less than the optimumamount required or if the mass is not agitated properly the bacterialactivity will not reach its maximum potential and the composting processwill require an unduly long period of time. In other words, if thetemperature of the mixture does not reach the maximum or optimum valueto allow the reaction to progress at its maximum potential rate theprocess becomes a costly one and the compost will not normally have arelatively high fertilizer value.

It has been recognized in the past that agitation and aeration of themixture is conducive to the rate at which the organic waste will beconverted to compost. In the past agitation of the mixture has beenaccomplished by such means as horizontally reciprocating or linearlymoving rakes or plows and rotary drums with or without baffles or radialfingers projecting into the mixture. With such types of equipment theproper aeration has not been achieved. For example, with rakes it isimpractical, if not impossible, to agitate the mass so that the oxygenin the air will come into intimate contact with all portions thereof forthe required time interval. In the case of rotary drums, some portionsof the mass remain stagnant for an unduly long period of time whileother portions are caused to fall or tumble rapidly through the airstream directed through the drum. In either case, substantially allportions of the mixture in the drum are not uniformly exposed to the airfor the required period of time to achieve the optimum operatingconditions to allow the reaction to progress at its maximum potentialrate and to produce the maximum nutrient content.

DISCLOSURE OF THE INVENTION

In accordance with the present invention a mixture or organic waste andorganic filler having a particular range of moisture, at least apartially particulate nature, and containing appropriate bacteria ischarged into a stationary composting chamber to partially fill thechamber. Within the chamber there is arranged a pair of horizontallyextending rotatable shafts. The shafts are spaced apart horizontally andeach is preferably provided with two rows of radially projectingagitating fingers arranged diametrically opposite each other and spacedapart lengthwise of the shaft. The fingers on each shaft have a lengthsuch that the outer ends thereof extend closely adjacent the adjacentside wall of the chamber. The two shafts are spaced apart a distanceless than twice the length of the fingers so that as the shafts rotatethe paths of travel of the outer end portions of the fingers on the twoshafts overlap at the central portion of the chamber between the shafts.The shafts are rotated in opposite directions so that the fingers sweepin a direction upwardly toward the longitudinal central portion of thechamber. The fingers in each row are spaced apart and the outer endsthereof are preferably interconnected by a tie bar so that, when the twoshafts are rotated slowly while air is directed through the chamber,substantially all portions of the mixture are gently agitated. Portionsof the mixture are progressively displaced toward the center of thechamber and slowly lifted and agitated in a manner such thatsubstantially all portions of the mixture are uniformly andprogressively exposed to the air flowing through the chamber for adesired period of time. The volume of air flowing through the chamber isadjusted to a relatively small amount such that, even thoughsubstantially all portions of the mixture are agitated slowly andexposed to the air so as to result in a relatively prolonged andintimate contact between the mixture and the air, the mixture is notcooled or substantially dried to a degree which would impair thethermophilic aerobic decomposition reaction.

BRIEF DESCRIPTION OF THE DRAWINGS

Other objects, features and advantages of the apparatus and method ofthe present invention will become apparent from the followingdescription and accompanying drawings, in which:

FIG. 1 is a top plan view of the composting apparatus of this inventionwith at least some of the access doors at the upper end thereof removed;

FIG. 2 is a side elevational view of the apparatus shown in FIG. 1;

FIG. 3 is a sectional view taken along the line 3--3 in FIG. 2; and

FIG. 4 is a sectional view taken along the line 4--4 in FIG. 3.

BEST MODE FOR CARRYING OUT THE INVENTION

The apparatus illustrated in FIG. 1 comprises a composting chamber 10and a drying chamber 12 which extend horizontally side by side. Each ofthese chambers has a bottom wall 14, side walls 16, end walls 18 and topwalls 20. These walls are preferably made of wood or other materialwhich has relatively good heat insulating properties. The major portionof the top wall of each chamber is divided into a plurality of covers orhatches 22 which are adapted to be lifted or otherwise opened to permitaccess to and inspection of the interior of the chambers. Within eachchamber there are arranged two shafts 24, 26. These shafts arejournalled at each end in the end walls 18 and are supportedintermediate their ends by horizontal braces 28 extending between theside walls of the chamber at generally the vertical midportion thereof(FIG. 3). Shafts 24a and 26a in composting chamber 10 are driven by anelectric motor 30 through a gear and chain drive 32. As shown in FIG. 3,shafts 24a, 26a are driven in opposite directions. Shafts 24b and 26b indryer chamber 12 are driven by an electric motor 34 through a gear andchain drive 36. Shafts 24b and 26b can be driven in either the same oropposite directions. Each of the shafts referred to has two rows ofradially extending fingers 38 thereon. As shown in FIG. 4, the fingersare preferably formed from angle iron. The two rows of fingers on eachshaft are arranged diametrically opposite one another and the fingersare spaced along the shaft in a spiral fashion. Between each of theintermediate braces 28 the outer ends of fingers 38 are interconnectedby spiral tie bars 40.

As shown in FIG. 3, the fingers 38 have a length such that, as theshafts are rotated, the tie bars 40 traverse a path closely adjacent thelower portion of side walls 16 and bottom wall 14. These wall portionsare generally semi-circular in cross section. It will be also observedfrom FIG. 3 that the spacing between the shafts in each chamber issubstantially less then twice the length of fingers 38 so that the pathsof travel of the outer end portions of the fingers overlap substantiallyin the space between the shafts. In order to obtain a more or lessconstant agitation of the mixture in the chambers and to prevent theinterference of the tie bars 40 the fingers 38 on one shaft arestaggered 90° circumferentially relative to the fingers on the othershaft at any one section of a chamber. Thus, when the fingers on shaft24a are disposed in a vertical plane the fingers on shaft 26a aredisposed in a horizontal plane. In the compost chamber 10 it isimportant that the two shafts 24a, 26a are rotated such that the fingerstend to displace the mixture in the chamber laterally inwardly andupwardly toward the central portion of the chamber as shown in FIG. 3.Thus, as viewed in FIG. 3, shaft 24a is rotated clockwise and shaft 26ais rotated counterclockwise. Fingers 38 are spaced apart on shafts 24a,26a a distance of between 7 to 12 inches. This spacing insures completeagitation and churning of the whole mass, which, because of its moisturecontent, is quite viscous, without lifting too much of the mixture asthe shafts are rotated. If the major portion of the mass is simplylifted by the fingers and then permitted to fall or roll downwardly overthe fingers, all portions thereof would not be brought into intimate andrelatively prolonged contact with the air flowing through the chamber.It is essential, therefore, that the fingers produce a substantialchurning action throughout the mixture so as to allow the air torepeatedly reach all parts thereof.

At one end thereof composting chamber 10 is provided with a manifold 42connected with an air intake 44 for admitting air to the chamber.Depending upon the length of chamber 10, one or more additional airinlets 46 may be provided along the side walls of the chamber. At theopposite end of the chamber there is provided an air outlet duct 48 towhich is connected a motor-driven fan 50 for exhausting air from thechamber. The flow of air through the chamber can be controlled by anysuitable means (such as dampers or the like) or by controlling the speedof motor-driven fan 50.

The spiral arrangement of the fingers 38 on the two shafts 24a, 26a isprovided to facilitate discharge of the compost from the chamber 10.When the two shafts are rotated at a proper speed the mixture isadvanced toward the end of the chamber opposite the drive 32. At thedischarge end of the chamber there is provided a discharge door 52operable by a hand lever 54. When the discharge door is open and theshafts 24a, 26a are rotated at the proper speed the contents of thecompost chamber are discharged into a trough 56 in which there islocated a feed auger 58 driven by a motor 60. Auger 58 feeds the compostto an inclined motor-driven conveyor 62 which discharges the wet compostinto one end of the drying chamber 12. At the adjacent end of chamber 12there is provided an air inlet duct 64 and at the opposite end thereofthere is provided an air outlet duct 66 in which there is located a highvelocity blower (not shown). The air outlet duct discharges the air fromthe dryer chamber and is connected to an acid trap for absorbing thenoxious gases and fumes from the discharged air.

The material to be composted is preferably entirely organic material.The material may be animal in origin, such as chicken, cow or hogmanure, slaughter-house scrap or the like; animal in origin such as hay,straw, paper, cardboard, corncob, cornstalk, brewer's yeast, or thelike; or mixed such as sewage sludge. The material preferably has amoisture content of 30-70% by volume. Fermentation will not proceed at areasonable rate in material that is too dry or too moist. Additionally,the material must have some particulate content so that it will becomeaerated as it is churned and agitated in the compost chamber 10. Ingeneral, a minimum of about at least 5-7% of the material by volume mustbe of a particulate nature, as opposed to a powdery, finely dividedstate. Finally, the mixture must contain aerobic bacteria and a portionof the aerobic bacteria must be thermophilic. The mixture preferablyalso contains anaerobic bacteria.

In general, the formulation of a proper charge for the compostingmachine will begin with a consideration of the organic waste materialthat is to form the basis for the charge. If that waste consists ofanimal waste such as manure, it will already contain the required formsof bacteria and the balance of the charge must consist of such organicmaterial as will provide the necessary particulate matter and bring thetotal moisture content within the range of about 30% to 70% by volume.Such organic filler material may typically constitute hay, straw,corncob, cornstalk, shredded paper, shredded cardboard, or sawdust. Thesawdust or the corncob will provide the necessary particulate elementsof the composition but if the other carbonaceous filler materials areused some sawdust or corncob or the like will have to be added to themixture.

When the basic waste matter is vegetable in nature it may be necessaryto add the necessary bacteria either directly or in the form of acertain percentage of animal waste containing the bacteria. For example,a desirable raw material for the process constitutes brewer's yeastreclaimed from a beer brewing process. Organic filler material whichwill absorb some of the natural excess moisture of the brewer's yeast tobring the total moisture in the batch to below 70% by volume, and willadd the particulate nature required for aeration, can be added, but theresultant mixture will still be lacking in the appropriate aerobic andthermophilic aerobic bacteria. These can be directly added to the batchor added in the form of animal waste containing these materials.

The following examples of charges for the composting process areillustrative of the range of possibilities:

EXAMPLE I

One part by volume chicken manure; one part by volume sawdust orcorncob. Hay, straw, shredded paper, shredded cardboard or cornstalkcould be substituted for most of the sawdust and a small proportion ofsawdust or corncob would have to be added to provide the required 5-7%by volume of particulate material.

EXAMPLE II

One part by volume sewer sludge; one part sawdust. The sawdust ispreferably 1/4 inch sieve size or larger. The sewer sludge contains therequired bacteria.

EXAMPLE III

One part by volume brewer's yeast refuse from a beer brewing processwith about 90% by volume moisture content; one part manure; one partsawdust and one part hay. The animal waste provides the necessarybacteria and the hay and the sawdust absorb the excess moisture from thebrewer's yeast to bring the total moisture volume under 70%, and thesawdust provides the necessary particulate matter.

EXAMPLE IV

Forty percent by volume produce waste (produce waste consists of scrapgreen vegetables and the like); 20% manure; 40% organic filler includingat least 15% particulate matter.

EXAMPLE V

One part paunch; i.e., the rumen or second stomach of cows are obtainedfrom a slaughterhouse, typically with each stomach containing 40 to 50pounds of undigested vegetable matter; 11/2 parts by volume sawdust.

Chamber 10 is preferably filled to a level just below the cross braces28, this level being indicated by the broken line 70 in FIG. 3. Afterthe compost chamber is so loaded covers 22 and hatch 68 are closed andthe flow of air and rotation of shafts 24, 26a are initiated. I havefound that by utilizing mixtures as described above excellent resultsare obtained when shafts 24a, 26a are rotated at between 1 revolutionper minute and 1 revolution every 6 minutes. Preferably with a mixturecontaining about 40% chicken manure and the balance sawdust the shaftsare rotated 1 revolution every 4 minutes. At the same time, it isimportant that the air flowing through the compost chamber is controlledin relation to the unit volume of the mixture in the compost chamber. Ihave found, for example, that, depending upon the nature of the mixture,the air flowing through the chamber should equal at least about 1/4cubic foot per minute (CFM) per ton, but should not exceed about 1 CFMper ton. The amount of air will vary between these limits depending uponits temperature and the moisture content and the nature and proportionsof the manure and sawdust. With a mixture comprising 40% chicken manureand 60% sawdust and having a moisture content of about 80% by weight, or40-50% by volume, I have found that the optimum air flow should be about1/2 CFM per ton. A ton of said mixture will vary in volume between about11/2 to 13/4 cubic yards, depending upon the mixture proportions and itsmoisture content. Accordingly, the air flow rates referred to may beconsidered to be a minimum of about 1/2 to 21/4 CFM per 100 cubic feetof mixture in the chamber. With the specific mixture and moisturecontent referred to above the preferred air flow rate is about b 1 CFMper 100 cubic feet of mixture.

When the composter is operated under these conditions and the airadmitted is at room temperature (at least 65° F.), the temperature ofthe mixture will gradually rise to between about 210° to 240° F. and onthe average to about 225° F. in a period of about 14 to 18 hours. Themixture will remain within this temperature range for about 8 to 10hours. Thereafter the temperature of the mixture will gradually decreasein about 8 to 9 hours to room temperature or at least to about 100° F.,at which time the speed of rotation of the shafts 24a, 26a increased toadvance the material in the compost chamber and discharge it throughdoor 52.

When shafts 24a, 26a are rotated at the relatively slow speedsmentioned, the relatively wet mixture in the compost chamber isthoroughly and slowly agitated. The fingers on each shaft rotatedownwardly through the mixture along the outer sides of the compostchamber and then upwardly in the space between the two shafts to gentlychurn the entire mixture. Since the fingers on the two shafts are offsetcircumferentially 90°, the fingers tend to lift and displace some of themixture laterally first in one direction and then laterally in theopposite direction so that the top of the mass assumes the configurationdesignated by broken line 72 in FIG. 3. This gently are repeatedagitation causes substantially all portions of the mixture to berepeatedly brought into intimate and relatively prolonged contact withthe air. However, the volume of air flowing through the chamber isrelatively small. Thus, there is no tendency for the air to cool themixture, and, since the compost chamber is formed of a material such aswood having good heat insulating properties, the mixture is capable ofbeing heated to the relatively high temperatures referred to (210° to240° F.) solely by the bacterial reactions occurring in the fermentationprocess.

Thus, by controlling the rate at which the mixture is agitated and therate at which the air flows through the composter within the aforesaidlimits, I have been able to produce a compost within a relatively shortperiod of time having a relatively high nutrient value. For example,when the mixture contains about 40% chicken manure and about 60%sawdust, under normal operating conditions the composting action iscompleted within a period of as little as 30 hours and the compost willhave a nitrogen content in excess of 7%, phosphorus about 31/2% andpotassium about 4 to 41/2%. This nutrient content is maintained providedthe compost is dried within a reasonably short period of time after itstemperature in the compost chamber starts to decrease. Thus, the mixturewill normally cool from the maximum temperature attained in thecomposting chamber (210° to 240° F.) down to about 100° F. or less inabout 8 to 9 hours. If the compost so produced is then promptlysubjected to a drying operation (within a matter of 2 or 3 hours), Ihave found that its nutrient content (particularly nitrogen) is notsubstantially diminished.

In order to prevent the initiation of the anaerobic reaction to anysubstantial extent following the aerobic reaction, it is necessary toreduce the moisture content of the compost to less than 50% by weight.Normally when the composting is completed in the composting chamber itwill have a moisture content of 55 to 65% when chicken manure is usedand slightly less with cow manure. This moisture content can be reducedto less than 50% in the drying chamber 12 within a period of not morethan 4 hours. However, other drying apparatus can be employed ifdesired. In the drying chamber 12 the two shafts 24b, 26b are rotated atapproximately 25 RPM and air is directed through the chamber in arelatively high volume. The air admitted to the drying chamber ispreferably at room temperature and in no event should it be hotter thanabout 120° F. If the temperature of the drying air exceeds about 120° F.it will promote the initiation of the anaerobic reaction which will tendto reduce the nutrient content of the finished product. After themoisture content of the compost in the drying chamber has been reducedto less than 50% by weight, a discharge door (not shown) at the driveend of the drying chamber is opened and the dried compost is dischargedto a conveyor 74. Conveyor 74 conveys the dried compost to a pulverizer(not illustrated). After the compost is pulverized it is promptlypackaged in plastic bags to prevent it from reabsorbing moisture whichwould tend to promote anaerobic decomposition. It will be appreciated,however, that, after the material is once dried, it will not reabsorbmoisture at a rapid rate. Thus, if it is simply stockpiled, after aperiod of days or even several weeks only the outermost layer of thestockpile will have absorbed a sufficient amount of moisture toappreciably decrease the nutrient content thereof.

While there is shown and described herein a specific form of composterand a specific form of dryer, it should be appreciated that theserepresent merely preferred embodiments. As mentioned previously, thefunction of the dryer is to reduce the moisture content of the compostedmaterial to below 50% rapidly by means of air at a temperature of notmore than about 120° F. Consequently, most any type of air dryer whichis capable of drying the compost within a reasonable period of time maybe employed. With respect to the composter, I believe it is essential toemploy two counter-rotating shafts with radially projecting fingersthereon. However, the number of fingers on the shafts, the spacingbetween the fingers, and the number of rows of fingers are not critical.As pointed out previously, the function of the fingers is to agitate andchurn the mass slowly and more or less constantly so that all portionsof the mixture are repeatedly brought into intimate and relativelyprolonged contact with the air. While the utilization of two rows offingers is preferred, it will be appreciated that more than two rows canbe employed. For example, if four rows of fingers were employed on eachshaft in composting chamber 10, then the speed of rotation of the shaftswould be half of those stated above and the air flow would remain at thesame rate as stated.

The resulting compost can be used as a soil conditioner or fertilizer oras an additive for animal feed. For example, when the composter ischarged with hog manure and fertilizer, the resulting compost can bere-fed to the hogs as a protein replacement at a rate in the range ofone pound per day per hod.

The high protein compost product may also be used as a soil for raisingmushrooms.

I claim:
 1. The method of producing a fermented product in ahorizontally elongated chamber having a pair of rotatable shafts thereinjournalled on generally horizontally extending parallel axes which arespaced apart in a horizontal plane, each shaft having at least one rowof radially projecting fingers thereon spaced along the axis of eachshaft, said fingers being located and dimensioned relative to saidchamber and the spacing of said shafts so that substantially the entirecontents of the chamber are agitated by the churning and lifting actionof the fingers when the shafts are rotated, which comprises:(a) loadinginto said chamber a batch of organic matter containing bacteria, saidbatch being of a predetermined volume such as to only partially fillsaid chamber and thereby provide a substantial air space throughout thelength of the chamber above the level of the batch mixture therein; (b)after loading, isolating said chamber from the surrounding atmosphereexcept for the hereinafter mentioned air flow; (c) rotating the twoshafts in opposite directions so that the fingers thereon travel throughthe mixture in a direction which tends to displace it from the oppositelongitudinal sides of the chamber laterally inwardly and upwardly towardthe longitudinal central portion of the chamber; (d) rotating the shaftat a rate such that the mixture is progressively agitated by thecircumferentially successive rows of fingers on each shaft about onceevery three minutes but not more than about once every one-half minuteto thereby cause substantially all portions of the mixture toprogressively come into intimate and relatively prolonged contact withthe hereinafter mentioned air; (e) while said shafts are rotating,conducting fresh air over the mixture through the entire length of saidchamber at a rate between about 1/2 to 21/4 cubic feet per minute perhundred cubic feet of the batch mixture in the chamber thereby causingfermentation of the mixture to proceed at such rate as to raise thetemperature of the mixture to about 210 degrees Fahrenheit within aperiod of not more than about 18 hours without the application ofexternal heat; (f) continuing the flow of air and rotation of saidshafts at said rates while and after the temperature thereof levels offat said elevated value to cool the moist fermented product so formed torelatively low temperature approaching room temperature; (g) drying thecooled moist product so formed using drying air of a temperature notexceeding 120 degrees Fahrenheit to reduce its moisture content to amaximum of not more than about 50% by weight within a reasonably shorttime after the aerobic reaction is completed and before substantialanaerobic decomposition of the fermented product occurs; and (h)maintaining substantially the entire batch of said product in said driedcondition until it is ready for use.
 2. The method called for in claim 1wherein the air is conducted through the chamber at about 11/4 cubicfoot per minute per 100 cubic feet of mixture.
 3. The method called forin claim 1 wherein the air admitted to the chamber is maintained at atemperature of at least about 65° F.
 4. The method called for in claim 1wherein the moist fermented product is cooled to a temperature of notmore than about 100° F. after its temperature levels off at saidelevated value.
 5. The method called for in claim 1 wherein each shafthas two diametrically opposed rows of teeth thereon and the shafts arerotated between about 1 and 1/6 r.p.m.
 6. The method called for in claim5 wherein the shafts are rotated at about 1/4 r.p.m.
 7. The method ofclaim 1 wherein the organic matter contains 30-70% by volume of waterand at least about 5% of particulate matter.
 8. The method of claim 1wherein the organic matter includes animal waste.
 9. The method of claim8 wherein the animal waste includes manure.
 10. The method of claim 9wherein the organic matter includes sawdust.